The present invention relates to an improvement to power trowling machines and, more particularly, relates to making the trowling machine lightweight and with fixed pitch spring steel blades, therefore making the machine very easy to use.
Trowling machines for finishing concrete or other surfaces have been known for many years. Common to these trowling machines are a centrally mounted power unit, such as an internal combustion engine, attached to a handle for holding and maneuvering the machine, a gear reducing unit connected to the power unit and a trowling assembly which rotates about a vertical axis beneath the power unit. The rotatable trowling assembly commonly comprises a hub mounted on a vertical shaft which is rotatable by the power unit through the gear reducing unit, and a plurality of trowling blade carriers in the form of arms extending radially from the hub. Typically, each carrier adjustably supports a trowling blade which extend radially and are usually inclined at a small pitch angle from the horizontal plane, with their trailing edges lowermost. The blades are effective to finish smoothly a surface of wet concrete or the like.
Exemplary of early trowling machines are U.S. Pat. No. 4,629,359 to Sengupta and U.S. Pat. No. 4,198,178 to Carlstrom et al. Both the Sengupta and the Carlstrom et al. patent disclose power trowels having adjustable pitched blades. U.S. Pat. No. 4,046,483 to Sutherland discloses a power trowel having an adjustable blade length and an adjustable blade pitch.
Traditionally, finishing concrete was a time consuming and delicate job. To create a desirable finish to the concrete, surface pores on the concrete must be closed by means of a trowling action either by hand or a trowling machine. The surface pores must be closed without disturbing larger aggregates that lie just below the surface that form a wearing plate. If this wearing plate is disturbed, the concrete will be subject to premature deterioration.
The previously mentioned known power trowels are typically of such a substantial weight that to place them on a wet concrete surface shortly after it has been poured will destroy the wearing plate and cause premature deterioration of the concrete. The operator must wait until the concrete substantially sets. Waiting for the concrete to substantially set up extends the finishing time, which in turn correlates to high labor costs wasted while waiting for the concrete to set. Also because of the size of the previously known power trowling machines, a substantial amount of operator strength is required to operate one of these machines. Furthermore, a great deal of experience and skill is needed to effectively operate them because the trowling blades of these known power trowling machines need to be adjusted in order to achieve a proper finish to the concrete. Each adjustment of the trowling blades has an effect on the finish of the concrete. Too steep of a pitch will dig too deeply into the wearing plate, thus causing premature deterioration of the concrete. Not enough pitch may not close the surface pores, thus creating a rough and incompletely finished surface.